8 puzzle solver using bfs

PHOTO EMBED

Tue Sep 26 2023 07:23:35 GMT+0000 (Coordinated Universal Time)

Saved by @ronin_78 #c++ 

from collections import deque

visited_states = []
total_moves = 70
expanded = 0
count = 0

class Node:
    def __init__(self, state, parent, operator, depth, cost):
        self.state = state
        self.parent = parent
        self.operator = operator
        self.depth = depth
        self.cost = cost

def create_node(state, parent, operator, depth, cost):
    return Node(state, parent, operator, depth, cost)

def expand_node(node):
    expanded_nodes = []
    
    temp_state = move_down(node.state)
    temp_node = create_node(temp_state, node, "down", node.depth + 1, node.cost + 1)
    expanded_nodes.append(temp_node)

    temp_state1 = move_up(node.state)
    temp_node1 = create_node(temp_state1, node, "up", node.depth + 1, node.cost + 1)
    expanded_nodes.append(temp_node1)

    temp_state2 = move_left(node.state)
    temp_node2 = create_node(temp_state2, node, "left", node.depth + 1, node.cost + 1)
    expanded_nodes.append(temp_node2)

    temp_state3 = move_right(node.state)
    temp_node3 = create_node(temp_state3, node, "right", node.depth + 1, node.cost + 1)
    expanded_nodes.append(temp_node3)

    return expanded_nodes

def move_left(state):
    swap = state.copy()
    idx = swap.index(0)
    if (idx == 0 or idx == 3 or idx == 6):
        return swap
    else:
        swap[idx - 1], swap[idx] = swap[idx], swap[idx - 1]
        return swap

def move_right(state):
    swap = state.copy()
    idx = swap.index(0)
    if (idx == 2 or idx == 5 or idx == 8):
        return swap
    else:
        swap[idx + 1], swap[idx] = swap[idx], swap[idx + 1]
        return swap

def move_up(state):
    swap = state.copy()
    idx = swap.index(0)
    if (idx == 0 or idx == 1 or idx == 2):
        return swap
    else:
        swap[idx - 3], swap[idx] = swap[idx], swap[idx - 3]
        return swap

def move_down(state):
    swap = state.copy()
    idx = swap.index(0)
    if (idx == 6 or idx == 7 or idx == 8):
        return swap
    else:
        swap[idx + 3], swap[idx] = swap[idx], swap[idx + 3]
        return swap

def bfs(start, goal):
    if (start == goal):
        return [None]
    else:
        to_be_expanded = []
        current_node = create_node(start, None, None, 0, 0)
        to_be_expanded.append(current_node)

        for i in range(total_moves):
            temp_expanded = []
            size = len(to_be_expanded)

            for j in range(size):
                if (to_be_expanded[j] in visited_states):
                    continue

                node_array = expand_node(to_be_expanded[j])

                for x in range(4):
                    if (node_array[x].state == goal):
                        count = i + 1
                        return node_array[x]
                    else:
                        temp_expanded.append(node_array[x])
                        visited_states.append(node_array[x].state)

            to_be_expanded.clear()
            to_be_expanded = temp_expanded.copy()
            temp_expanded.clear()

    return None

def main():
    method = 'bfs'
    length = 0
    x = 0
    x = x + 1

    board_input = input("Enter the initial state values (comma-separated): ")
    board_split = board_input.split(',')
    starting_state = [int(i) for i in board_split]

    goal_input = input("Enter the goal state values (comma-separated): ")
    goal_split = goal_input.split(',')
    goal_state = [int(i) for i in goal_split]

    if (len(starting_state) == 9 and len(goal_state) == 9):
        result = bfs(starting_state, goal_state)
        if result == None:
            print("No solution found")
        elif result == [None]:
            print("Start node was the goal!")
        else:
            print("Total number of moves needed =", result.cost)
            path = []
            path.append(result.state)
            current = result
            flag = True

            while flag:
                parent = current.parent
                prev_state = parent.state
                path.append(prev_state)
                current = parent

                if (prev_state == starting_state):
                    flag = False

            path.reverse()
            print("Step-wise Sequence of states from start to goal is ")
            for state in path:
                print(state[0], "|", state[1], "|", state[2])
                print(state[3], "|", state[4], "|", state[5])
                print(state[6], "|", state[7], "|", state[8])
                print()
    else:
        print("Invalid input")

if __name__ == "__main__":
    main()
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